Supplied air respirators are regularly worn in environments where the surrounding air contains contaminants. Clean air is delivered to the wearer from a supply tank or from a powered air source that drives the ambient air through an air filter.
Systems that use a powered air source to supply clean air to the wearer are referred to as powered air purifying respirators—known shorthand as “PAPRs”. PAPRs typically have two main parts: a facepiece and a filtering unit. The facepiece is worn at least over the nose and mouth of the user (it also may cover the eyes and ears), and the filtering unit is commonly worn about the user's waist. The filtering unit often includes filter cartridges, a housing, a fan, and an electric motor that drives the fan. The fan and motor are contained within the housing, and the filter cartridges are attached to the housing body. Ambient air is filtered by being forced through filter elements that are contained within the filter cartridges. This filtered air is then delivered to the facepiece through a hose. The electrically powered fan drives the air from the filter cartridges, through the hose, and into the facepiece interior. Because the fan does the work required for air movement through the PAPR system, the user is able to comfortably receive a clean supply of air with little effort.